INTEXT QUESTIONS 26.1
1. A chemical substance may occur as an element, mixture or compound. To which category does air belong?
Answer: Air belongs to the mixture category because it contains different gases physically mixed together, not chemically combined.
2. Name the major constituents of air. Which constituents are inevitable for survival of plants and animals?
Answer: Major constituents of air are nitrogen and oxygen.
The constituent inevitable for survival of plants and animals is oxygen.
3. If you were to compare the relative amounts of nitrogen and oxygen in the atmosphere. Which will be four times the other?
Answer: Nitrogen is about four times the amount of oxygen in the atmosphere .
4. Air also contains water vapour. But is its percentage in air the same at all places?
Answer: No, the percentage of water vapour in air is not the same at all places. It varies from place to place depending on climate and weather conditions.
INTEXT QUESTIONS 26.2
1. Why is oxygen essential for life? What would happen if there is no oxygen in air?
Answer: Oxygen is essential for life because it is needed for respiration in plants and animals to release energy from food. If there is no oxygen in air, animals would die and life would not survive.
2. Carbon dioxide acts as food for plants. Name the process in which it is utilized for making food.
Answer: Carbon dioxide is used by plants to make food through the process of photosynthesis.
3. What is dry ice and what is it used for?
Answer: Dry ice is the solid form of carbon dioxide (CO₂). It is used as a refrigerant to keep things cold, especially during storage and transport of food and other materials.
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